56v battery not charging. Could it be the charger? Charger light reads 25% then eventually shuts down.

Just like title says, can't get battery charged. I put two different 2.5ah batteries on the fast charger and the same thing happens. The charger immediately turns on, fan turns on, and green light on charger reads 25%. It runs like this for several minutes and then just shuts down. I get no light on the battery when I press the status light button. Could this be my charger? I initially thought battery but with two different batteries resulting in the same symptoms, it makes me think it could be the charger.